Modern jet engines commonly include a pair of thrust reverser ducts or cowls which, during aircraft operation, define the outer wall of the engine exhaust nozzle. Such thrust reverser ducts must be capable of withstanding considerable loads caused by the high pressure of the jet exhaust stream which it contains. The thrust reverser ducts are normally hingedly connected to the upper portion of the nacelle near the point where the nacelle is attached to the engine support strut. The ducts can be pivoted upwards about their hinge points to provide access to the engine for maintenance and repair. For aircraft operation, the ducts are pivoted downwards into closed positions in which their lower ends are adjacent to one another, or adjacent to an interposed strut, services channel or bifurcation. The closed ducts are then secured by latches to form a continuous circumferential load bearing structure.
The design of latches for thrust reverser ducts is complicated by a number of factors. For example, thrust reverser ducts must have an appreciable thickness in order to accommodate flow reversing cascades, and the inner surfaces of the ducts must include a load bearing member or ring to withstand the aforementioned loads due to internal pressure. Furthermore, a large circumferential force must be applied during latching to ensure satisfactory flange seating. The hinge line of the ducts, however, must be adjacent their outer surfaces to avoid interference with adjacent structure when the ducts are opened. As a result, a latch system for such thrust reverser ducts must include upper latches for latching together the upper ends of the load bearing rings near the top of the nacelle, as well as lower latches for connecting the lower ends of the load bearing rings to form a continuous circumferential load bearing structure. The upper latches of such a system are quite inaccessible. They are not only located inboard of the outer surface of the nacelle, but in a typical airplane installation they are a considerable distance above the ground as well. In the past, complex mechanical linkages or electrical actuators have been required to permit such latches to be locked and unlocked from ground level. Furthermore, since the latches are not visible when the ducts have been closed, means have been required for enabling maintenance personnel to confirm that the latches are locked after the ducts have been closed. In practice it is desirable that the upper latch system be nondisengaging because of its inaccessibility but the lower latch system must disengage.